CN101490819B - Ultrashort laser pulse wafer scribing - Google Patents

Abstract

Systems and methods are provided for scribing wafers (200) with short laser pulses so as to reduce the ablation threshold of target material. In a stack of material layers (202, 204, 206, 208), a minimum laser ablation threshold based on laser pulse width is determined for each of the layers (202, 204, 206, 208). The highest of the minimum laser ablation thresholds is selected and a beam (216) of one or more laser pulses is generated having a fluence in a range between the selected laser ablation threshold and approximately ten times the selected laser ablation threshold. In one embodiment, a laser pulse width in a range of approximately 0.1 picosecond to approximately 1000 picoseconds is used. In addition, or in other embodiments, a high pulse repetition frequency is selected to increase the scribing speed. In one embodiment, the pulse repetition frequency is in a range between approximately 100 kHz and approximately 100 MHz.

Description

Ultrashort laser pulse wafer scribing

Technical field

The application relates to laser cutting or delineation, particularly excises the method for the manufacturing integration circuit of material under high-repetition-rate with utmost point short laser pulse.

Background technology

Integrated circuit (IC) usually is manufactured on silicon substrate or forms array.IC comprises many layers that are formed on substrate usually.Can use mechanical saw or laser that one or more layers are removed.After delineation, make circuit member separated from one another with saw or laser, substrate can be cut and be worn, and sometimes also is known as to cut (dicing).

Semiconductor manufacturers has been dwindled the size of transistor in IC, to improve the usefulness of chip.This causes the raising of speed and component density.In order to promote further to improve, semiconductor manufacturers uses material to reduce the electric capacity of dielectric substance layer.For instance, in order to form circuit pattern preferably, the semiconductor wafer that will have low dielectric constant (low k) isolation layer is laminated on the surface of semiconductor substrate.Low k dielectric medium can comprise for example inorganic material (SiOF or SiOB for instance) or organic material (polyimide-based or Parylene based polyalcohol for instance).

Yet machine cuts commonly used or laser cutting method are not fit to delineate many pre-processed wafers (for example, low k dielectric material) very much.Relatively low density, lack mechanical strength and to the susceptibility of thermal stress, make low k dielectric material counter stress very responsive.Known is, mechanical wafer commonly used is cut the defective that causes the breaking of low-k materials, crack and other type with the delineation technology, therefore destroys the IC element.In order to reduce problems, need reduce cutting speed.Yet this has seriously reduced productivity ratio.

Moreover the laser technology of knowing can produce excessive heat and chip.Traditionally, use tens psecs or higher laser pulse width to be used for semiconductor cutting or delineation.Yet so long pulse width causes excessive thermal diffusion, thereby causes heat affected area, oxide layer double teeming, excessive chip and other problem.For instance, Fig. 1 is the side view schematic of using laser cutting technique commonly used that semi-conducting material 100 is cut.Near cutting zone 102, form heat affected area 104 and recast oxide layer 106.The crack can be formed in heat affected area 104, and reduces the breaking strength (die break strenth) of semi-conducting material 100.Therefore, reliability and yield reducation.Moreover, the surface that the chip 108 that comes from cutting zone 102 disperses to spread all over semi-conducting material 100 everywhere, and meeting, for instance, pollution connection gasket (bond pad).

In addition, laser cutting section commonly used can suffer the groove backfill of the material that the laser splash goes out.When the thickness increase of wafer, this backfill meeting becomes more serious and reduces the speed of cutting.Moreover in many process conditions, for many materials, the backfilling material that splash goes out can more be difficult to be removed in process subsequently compared with initial target material.Therefore, will destroy IC element and the extra cleaning that need to carry out the element on substrate and/or extensively separate if produce low-quality cutting.

Therefore, increase productivity ratio and improve cutting surfaces or the method for kerf quality is desirable with laser cutting or delineation.

Summary of the invention

The system and method for the completed wafer of delineation is provided at each execution mode of this announcement, and this wafer comprises low k dielectric medium and/or other material, and the method is the same with already present machinery and/or laser means fast or faster.Yet this laser grooving and scribing is in the situation that reduce or there is no machinery and/or thermal stress and reduction or do not have chip to carry out.Therefore, needs seldom or not need cleaning procedure afterwards.And, form clean, cutting straight border, do not need element on wafer is carried out extra lateral separation, be suitable for delineating technique.

In one embodiment, provide cutting to be formed on the method for the plurality of layers on substrate.Every one deck in plurality of layers has Laser Ablation Threshold (ablation threshold) separately, and Laser Ablation Threshold is different along with laser pulse width.The method comprises for the every one deck in plurality of layers determines the minimum laser ablation threshold, and selects soprano in the minimum laser ablation threshold.The method also comprises the one or more laser pulse beams of generation, the laser pulse beam has the energy density scope between the selected Laser Ablation Threshold of selected Laser Ablation Threshold and about 10 times, and delineates otch being formed between a plurality of integrated circuits of plurality of layers.This otch passes plurality of layers until the upper surface of substrate.

In specific execution mode, the pulse width range that laser pulse has in about 0.1 psec (picosecond) to 1000 psecs.Moreover beam has pulse recurrence rate, its scope in about 100 KHz between about 100 MHz, and can be with scope in about 200 mm/second to the speed between about 1000 mm/second, cut and wear the material of about 10 microns.In addition, then in other execution mode, the energy range of each pulse is between about 1 little joule to about 100 little joules.

In another embodiment, provide the method for wafer scribing, on this wafer or wherein be formed with a plurality of integrated circuits.Integrated circuit is separated by one or more roads.The method comprises the one or more laser pulse beams of generation.Select the pulse duration of laser pulse, make the ablation threshold of target material minimize.The method further comprises the target material of an ablation part, and the range of pulse repetition frequency of its beam is being approximately 5.1 MHz between about 100 MHz.

In another embodiment, provide to comprise the method that produces one or more laser pulse beams, this laser pulse has pulse duration, its scope in about 0.6 psec between about 190 psecs.The method further comprises the target material with a beam ablation part.

In another embodiment, provide to comprise the method that produces one or more laser pulse beams, this laser pulse has pulse duration, its scope in about 210 psecs between about 1000 psecs.The method further comprises the target material with a beam ablation part.

To put down in writing in ensuing preferred implementation other aspect and advantage, continue along with the reference accompanying drawing to launch.

Description of drawings

Fig. 1 is the side view schematic when using laser cutting technique commonly used with cutting semiconductor materials.

Fig. 2 A-2C is the side view schematic of the example workpiece through cutting of specific implementations according to the present invention.

Fig. 3 A is the perspective view of the work piece cut of another execution mode according to the present invention.

Fig. 3 B is the side view schematic of the workpiece shown in Fig. 3 A.

Fig. 4 illustrates the Gaussian beam irradiance profile of ground simplicity of explanation and the difference between the beam irradiance profile of adjustment of simplification.

The difference between the beam cross-section waveform is explained on Fig. 5 A-5C diagram ground.

Fig. 6 A-6D is according to specific implementations of the present invention, and exemplary demonstration is by passing diffraction optical assembly (diffractive optical element; DOE) gaussian beam of propagating produces radiates form in fact uniformly.

Fig. 7 shows the electron micrograph of delineating the otch that passes interconnection and low k dielectric radio layer according to the embodiment of the present invention.

Fig. 8 roughly explains continuously workpiece is being placed under laser pulse on cut direction according to the embodiment of the present invention.

Fig. 9 is according to the embodiment of the present invention, uses the electron micrograph of micromechanics pattern in semi-conducting material of laser ablation methods.

Figure 10 is according to the embodiment of the present invention, uses the electron micrograph of micromechanics pattern in semi-conducting material of laser ablation.

Embodiment

The ability of material absorbing laser energy determines that this energy can carry out the degree of depth of ablation.Ablation depth is that the evaporation temperature by the absorption degree of depth of material and material decides.The duration of by control example such as wavelength, pulse duration, the parameter of pulse repetition frequency and beam quality, improve the quality of cutting speed and cutting surfaces or otch.In one embodiment, select one or more in these parameters, enough low energy density (usually measuring with joule/square centimeter) is provided, just have the energy of enough ablation target materials.Therefore, can reduce or eliminate the energy total amount that excessive deposition enters material.Use than low energy densities reduce or eliminate recast oxide layer, heat affected area, break, crack and chip.Therefore, breaking strength and required rear laser cleaning total amount decline have been improved.

The people such as Mourou are at United States Patent (USP) the 5th, 656, and point out in No. 158: the ablation threshold of material is the function of laser pulse width." ablation threshold " is term widely as used herein, and it comprises usually and customary meaning, and for instance, comprise an enough institute must energy density to remove for delineation or the material that cuts.In traditional pulse duration of nano-seconds, compared with than short pulse width, the ablation threshold of usually having relatively high expectations.Improve peak power and reduce the heat conduction than short pulse.In order to increase spatial resolution, the people's such as Mourou patent discloses the pulse duration of the scope of application at thousand part per trillion second (femtosecond).Yet, the laser pulse width of thousand part per trillion seconds, compared with traditional nanosecond pulse, each pulse removes material in a small amount.Therefore, the time total amount of required cutting or delineation line increases and productivity ratio decline.Moreover in the pulsating sphere of thousand part per trillion seconds, ablation threshold can shorten and increase along with the pulse of thousand part per trillion seconds.

Therefore, in the execution mode that this discloses, pulse duration is selected at the scope of psec at one, and reducing ablation threshold, and compared with the pulses of thousand part per trillion seconds, every pulse removes more materials.In the scope of psec, the time constant that is used at first the electronics that excited by laser pulse and body of material positive energy exchange (electronics and continuous electronic-lattice interaction and thermalization) for instance, is the scope in psec.For instance, time constant can be the order of magnitude of about 1 to 10 psec.Therefore, think shorter pulse or the pulse persistance that adapts during cause " cold " coulomb type ablation and without obvious heat.Therefore, thermal stress and/or the melting of material have been reduced or eliminated.

The technical staff will be appreciated that according to the record here, if the scope of pulse can cause some pattern of fever ablations in about 1 psec between about 10 psecs.But, use every pulsion phase to low energy density, it is only slightly higher than ablation threshold, just can reduce the excessive energy that produces melted debris.Therefore, can form cleaner otch.Further, thermal impact is limited in laser spot usually, and because pulse duration is very little, heat can't spread or be transmitted to beyond radiation areas.Yet, when pulse becomes too small, diminish with the effective depth of the interactional laser of material, and the Efficiency Decreasing of ablation (electronics that is excited by laser pulse at first for instance, tails off).

In specific implementations, in order to increase cutting speed, the strobe pulse repetition rate provides the cutting speed of conventional saw or laser semiconductor cutting technique.Excise fast material with high pulse repetition frequency.Moreover high pulse repetition frequency provides more multi-energy, is used for ablation before material around at energy dissipation.

As hereinafter detailed discussion, in specific implementations, set beam shape and improve kerf quality.For instance, laser beam can be set shape and create for example smooth in fact kerf bottom, and its kerf bottom produces less chip and reduction or elimination to the destruction of substrate.Except improving sidewall profile, beam shape has also reduced the width of recast oxide layer.

For convenience; cutting vocabulary usually can be used for comprising delineation (do not penetrate the entire depth of target workpiece and cut) and cut and wear, and it comprises thinly slices (usually relevant with the cutting crystal column) or cut (dicing) (usually and be divided into partly relevant by crystal column).Thinly slice or cut interchangeable in this article.

With reference now to accompanying drawing,, in its accompanying drawing, similar reference number represents similar assembly.Clearly illustrate future, the first bit digital of reference number refers to the numbering of accompanying drawing, and wherein corresponding assembly is used at first.In ensuing description, can provide numeral specific details, to understand the execution mode in this announcement fully.Yet those skilled in the art will be appreciated that the present invention can be implemented and not need one or more specific detail or other method, member or material.Further, in some cases, do not show or be described in detail known structure, material or operation, to avoid fuzzy idea of the present invention.Moreover described feature, structure or characteristic can be combined in any suitable method with one or more execution modes.

Fig. 2 A-2C is the side view schematic of the example workpiece through cutting of specific implementations according to the present invention.Workpiece 200 comprises the layer 202,204,206 that is formed on substrate 208.To understand as the technical staff, layer 202,204,206 can comprise the interconnection layer (comprising low k dielectric medium) that is insulated layer and separates to form electronic circuit.For instance, layer 202,204,206 can comprise for example Cu, Al, SiO ₂, SiN, fluorosilicate glass (fluorsilicated glass; FSG), organic silicate glass (organosilicatedglass; OSG), SiOC, SiOCN and other are used in the material that IC makes.In order to illustrate, shown three layer 202,204,206 in Fig. 2 A-2C.Yet the technical staff will understand that, more layer or less layer can use in specific IC.As shown, substrate 208 comprises Si.Yet the technical staff also will understand that, other useful material in IC makes can be used in substrate 208, for instance, comprises glass, polymer, metal, composition and other material.For instance, substrate 208 can comprise FR4.

Electronic circuit is formed on active component zone 210,212, and it is by delineation line or road 214 and separated from one another.What the technical staff will understand that is, among test structure often is formed on 214 or on every side.In order to create independently IC, workpiece 200 prolonging road 214 be scored, cut wear or both.In Fig. 2 A, delineate workpiece 200 according to laser beam 216 demonstrations of an execution mode by ablation layer 202,204,206 in the zone in road 214.As shown in Fig. 2 B, the result of laser grooving and scribing process be laser cut 218 from the upper strata 202 upper surface across-layer 202,204,206 until the upper surface of substrate 208.As described below, in specific implementations, laser beam 216 is set shapes, make the mass penalty of otch sidewall profile, and reduce or avoid destruction to substrate 208.

Laser beam 216 comprises a series of laser pulse, through construction with provide minimum may energy density to workpiece 200, but still provide required layer 202,204,206 and/or the material ablation of substrate 208.In one embodiment, select the energy density of laser beam 216, make scope between about ten times of the ablation threshold of the ablation threshold of workpiece 200 and workpiece 200.In another embodiment, select the energy density of laser beam 216, make scope between about five times of the ablation threshold of the ablation threshold of workpiece 200 and workpiece 200.

According to an execution mode, in order to reduce ablation threshold, pulse duration be set up scope in about 0.1 psec (picosecond) to 1000 psecs.In other execution mode, pulse duration is set up scope in about 1 psec to 10 psec.In other execution mode, pulse duration is set up scope in about 10 psec to 40 psecs.Yet the technical staff will can use other pulse duration from recognizing also disclosing of this.For instance, in one embodiment, the scope of pulse duration is in about 0.6 psec to 190 psec, and at another execution mode, the scope of pulse duration is in about 210 psec to 1000 psecs.

In one embodiment, the average energy scope of use is between about 10 watts to about 50 watts, and the energy range of every pulse produces laser beam 216 between about 1 little joule to about 100 little joules.When the scope of layer 202,204,206 aggregate thickness is between about 8 microns to about 12 microns the time, laser beam 216 is used high pulse repetition frequency through construction, with velocity interval in about 200 mm/second between about 1000 mm/second, cut and wear layer 202,204,206.

In specific implementations, the scope of the layout between pulse is between about 1 nanosecond nanosecond to 10, so that basically complete the dissipation of heat.In other embodiments, the scope of the layout between pulse about 10 nanosecond to 1 microsecond between so that pat formerly pulse through the excision material, to diffuse to enough low-density, make itself and subsequently pulse not have obvious interference.In specific this type of execution mode, the scope of pulse repetition frequency in about 1 MHz between about 100 MHz.In other execution mode, the scope of pulse repetition frequency in about 5.1 MHz between about 100 MHz.In another embodiment, the scope of pulse repetition frequency in about 50 KHz between about 4 MHz.

At high pulse repetition frequency (for instance, more than about 1 MHz, more specifically, more than about 10 MHz), the residual impulse energy can with the form accumulation of heat, not dissipate between pulse because the energy that deposits does not have time enough.Cumulative effect usually increases ablation efficiency and also can increase thawing.Yet thawing is limited in the radioactive area usually, and is concentrated in the center of otch.Depend on specific application, melt in otch center increase and can improve or reduce the desirable quality of otch.

In the example execution mode, the Duetto that use can obtain from the Time-Bandwidth of Switzerland Zurich ^TMLaser produces laser beam 216.Duetto ^TMLaser has the wavelength of about 1064 nanometers, the scope of pulse repetition frequency in about 50 KHz between about 4 MHz, the scope of average energy is at about 10 watts or more, the peak-peak energy is approximately 16 megawatts, little joule of the energy of each pulse the highest about 200, and the highest about 12 psecs of pulse duration.Alternatively, in other example execution mode, " RAPID " picosecond laser that use can obtain from the Lumera-Laser GmbH of German Kaiserslautem produces laser beam 216.

The harmonic wave of 1064 nanometer lasers also can be used for improving the ablation for certain material.For instance, the wavelength of about 532 nanometers can be used for excising Cu, and the wavelength of about 355 nanometers can be used for excising Si and specific low k dielectric medium, and the wavelength of about 266 nanometers can be used for excising glass.In one embodiment, at least partially according to layer 202,204,206 and/or material separately and the relative thickness of substrate 208 select wavelength, make cutting speed rise.For instance, wavelength can be optimised, to excise thick Cu layer but not the dielectric layer of relative thin.In substituting execution mode, wavelength can be between the ablation of one or more layer 202,204,206 and/or substrate 208 and be changed.The technical staff also will understand that, uses harmonic wave also will improve the ability of laser focusing beam, is to depend on wavelength because focus on.

According to an execution mode, in order to delineate layer 202,204,206, during wavelength, pulse energy and the pulse persistance set, the energy density of each laser pulse is set to ablation threshold in the lamination of layer 202,204,206 or more than ablation threshold.In one embodiment, the energy density of each laser pulse is arranged on the scope between about a times to ten times of ablation threshold in lamination.In other embodiments, the energy density of each laser pulse is arranged on the scope between about a times to five times of ablation threshold in lamination.

For instance, can determine that the 3rd layer 206 to the first and second layers 202,204 have higher ablation threshold.Therefore, use the short pulse in picosecond range, the energy density of laser pulse is set can excise the 3rd layer 206, also can make ground floor and the second layer 202,204 ablations.In the execution mode of example, energy density is arranged on about 1.5 times of ablation threshold in lamination.For instance, suppose that the 3rd layer 206 has pulse duration at the ablation threshold of about 10 joules/square centimeter of about 10 psecs, laser beam 216 is constructed into the about 20 little joules of pulses that produce the spot definition with about 10 microns, with the scope of reaching energy density at about 15 little joules/square centimeter between about 20 little joules/square centimeter.

The technical staff will be appreciated that, in the laser grooving and scribing program, more layer or layer still less can cut or part excisions.For instance, laser beam 216 excises upper two-layer 202,204 and do not excise the 3rd layer 206 through construction.Alternatively, as shown in Fig. 2 C, laser beam 214 can be come complete incised layer 202,204,206 and substrate 208 through construction, fully to make active component zone 210,212 (cutting for instance) separated from one another.In specific implementations, silicon substrate has the scope of thickness between about 10 microns to about 760 microns, uses laser cutting technique and cuts and wear.The technical staff will understand from the announcement at this, and other substrate thickness also can be worn according to cutting in the method for this narration.

Yet as shown in Fig. 2 A and 2B, in one embodiment, workpiece 200 is scored to remove the layer 202,204,206 of at least a portion in road 214.Then, workpiece 200 can prolong otch path 218 and mechanically splitting or mechanically cut, to complete the step of cutting.Therefore, material (it can and/or can destroy saw for instance by saw, low k dielectric medium or test structure) can be removed before cutting.In one embodiment, saw is along otch 218, so that contact layer 202,204,206 not.Advantage ground, crack and chip reduce, and breaking strength increases, and overall yield is improved.

Fig. 3 A is the perspective view of workpiece 300 cuttings of another execution mode according to the present invention.Workpiece 300 comprises the layer 302,304 that is formed on substrate 306.As previously mentioned, for instance, layer 302,304 can comprise material for example Cu, Al, SiO2, SiN, fluorosilicate glass (fluorsilicated glass; FSG), organic silicate glass (organosilicated glass; OSG), SiOC, SiOCN and other use are at the material of the material of IC manufacturing.For instance, substrate 306 can comprise the material that Si, FR4, glass, polymer, metal, composition material and other use are made at IC.

Fig. 3 B is the side view schematic of the workpiece shown in Fig. 3 A.As shown in the figure, electronic circuit is formed on active component zone 308,310, its with road 312 with separated from one another.In this example, workpiece 300 uses and is scored at this laser parameter of describing, and makes laser cut 314,316 be formed on 312 both sides.In one embodiment, each laser cut 314,316 scope are between about 5 microns to about 10 microns wide.As shown in Fig. 3 A and 3B, in specific implementations, laser cut 308,310 extends to substrate 306.Yet in other execution mode, laser cut 308,310 is removing materials in layer 302,304 one or both only.

In operation further, laser grooving and scribing 314,316 is as for " cracking obstacle " or the barriers of physical property of heat with mechanical stress.Therefore, laser grooving and scribing 314,316 be provided at 312 with active component zone 308,310 between machinery separate and thermal release.For instance, use laser ablation technology described herein and after forming laser incising line 314,316, road 312 can mechanically cut active component zone 308,310 is cut into small pieces.Cut 312 abominable effect and be not transmitted to active component zone 308,310, make to machinery and cut relevant crack and chip in this area decreases or elimination.

As mentioned above, in specific implementations, be presented at adjusted (control) shape of laser beam 216 of Fig. 2 A, in order to improve quality and the minimizing of otch sidewall profile or prevent from destroying substrate 208.The difference between adjustment beam irradiance profile 404 that Fig. 4 illustrates the Gaussian beam irradiance profile 402 of ground simplicity of explanation and simplifies.When with through adjusting beam irradiance profile 404 relatively the time, the center of Gaussian beam irradiance profile 402 is also large many compared with evaporation threshold value 406 and melting threshold 408.Therefore, gaussian beam discharges a large amount of excess energies to target material, particularly at the center of beam.

Moreover, Gaussian beam irradiance profile 402 in melting threshold 408 and evaporation the slope between threshold value less than through adjusting beam irradiance profile 404 at melting threshold 408 and the slope that evaporates between threshold value.Therefore, gaussian beam can produce wider recast oxide layer, but can be evaporated because the wide region of material will not be melted.For instance, the width of arrow 410 expression recast oxide layer is produced by gaussian beam, and the width of arrow 412 expression recast oxide layer is by being produced through adjusting beam.Due to through adjusting the fast-ramping of beam radiation outline shape 404 between melting threshold 408 and evaporation threshold value 406, produce narrower recast oxide layer through adjusting ray.

The difference between the beam cross-section waveform is explained on Fig. 5 A-5C diagram ground.Fig. 5 A demonstration Gauss cross section waveform 510.Fig. 5 B-5C shows the cross section waveform of " carnival hat " shape.Fig. 5 B shows square cross section waveform 512, and Fig. 5 C shows circular cross section waveform 514.

The people's such as Dunsky United States Patent (USP) has disclosed with the 6th, 791, No. 060 the System and method for of determining beam shape according to specific implementations the 6th, 433, No. 301.Fig. 6 A-6D exemplarily shows the irradiance profile in fact uniformly that is produced by gaussian beam, and this gaussian beam passes as United States Patent (USP) the 5th, 864, (the diffractive optical element of the diffraction optical assembly shown in No. 430; DOE) propagate.Fig. 6 A-6D shows " carnival hat " shaped beam.Fig. 6 A-6C shows square irradiance profile, and Fig. 6 D shows columniform irradiance profile.The irradiance profile of Fig. 6 C is " turning upside down ", is presented at its edge compared with having higher density towards its center.Controlling the beam shape member can be selected, and has the pulse of the radiation outline shape that turns upside down with generation, and as shown in Fig. 6 C, its outside at broken broken line 610 is cut into thin slice to promote ablation, further improves the otch tapering.What the technical staff will understand that is, control the beam shape member can be designed to provide many may be to the irradiance profile of useful other of application-specific.

Fig. 7 shows that delineation passes the electron micrograph of the otch 700 of interconnection and 702 layers of low k dielectric mediums.Otch 700 is about 35 microns wide and delineate with the laser with about 355 nano wave lengths.As said, short pulse width (for instance, in the scope of picometre) and fast-pulse rate frequency can be used to realize the low energy densities ablation in two-forty.Otch 700 is surpassing the speed of 500 mm/second, is scored with the beam of " carnival hat " shape.Beam shape provides smooth in fact kerf bottom, and vertical in fact and by the good side of determining.Further, there is no in fact chip or crack.

In the specific implementations of this announcement, delineation can be used single laser operations and complete.Yet in specific other execution mode, in a laser operations, the always amount of removing of the material of every pulse not fully reaches the desirable delineation degree of depth.In specific this type of execution mode, be to expose with a plurality of pulses in each position of delineation line, remove to reach desirable material.In this type of embodiment, pulse on cut direction on material to stack.

For instance, Fig. 8 roughly explains continuously workpiece 800 is being placed under laser pulse on cut direction according to the embodiment of the present invention.Each pulse ablates certain spot size 802 is to pulse ablation depth.In order to reach whole ablation depth, pulse subsequently has overlapping skew or the bite size 804 in cut direction.For instance, the first pulse removes in the first area 806 material.Then, (for instance, the left side to Fig. 8) moved in the second pulse in cut direction, to remove the additional materials that comes from second area 808 and the 3rd zone 808 '.Second area 808 and the 3rd zone 808 ' (when in conjunction with the time) width be that width with first area 806 is when identical (for instance, spot definition 802).Second area 808 is the side of the first area 806 in cut direction and the width with bite size of being same as 804.The 3rd zone 808 ' is under a part of first area 806.Therefore, along with the first pulse increases to the second pulse overall ablation depth.

Be applied to along with more pulse on the workpiece 800 of cut direction, thereby continue the delineation step.The degree of depth of integral cutting increases along with each pulse, until reach the desirable degree of depth 810.After the desirable degree of depth 810 reached, extra pulse persistance did not make it to surpass the desired degree of depth 810 at the cut direction removing materials and do not increase overall depth.For the spot definition 802 of an appointment, bite size 804 will define the desired degree of depth 810.The pulse ablation depth that the desired degree of depth 810 equals Sing plus multiply by the ratio of spot definition 802 and spot definition 804.For instance, as shown in Figure 8, bite size 804 is approximately the size of 1/7 spot definition 802.Therefore, the desired degree of depth 810 pulse ablation depth (and just can reach after seven wavelength) that is Sing plus of seven times.

In one embodiment, control during the pulse persistance as above of cutting speed by selection at first, to reduce ablation threshold.Advantage ground, in specific implementations, pulse duration is selected to provide in fact for the minimum ablation threshold of target material.Then, the selective light spot size provides desirable energy density with the energy for selected every pulse.Then, based on the Sing plus ablation depth, select bite size so that overall ablation depth to be provided.As mentioned above, then, the strobe pulse repetition rate is to improve cutting speed.In specific implementations, than low pulse repetition frequency (for instance, about 70 KHz) be with high pulse energy (for instance, about 50 little joules to about 100 little joules) use together, to arrive asymmetric (ellipse or rectangle for instance) by the length-width ratio that changes laser spot from symmetrical (circle for instance), come ablation in low energy densities and two-forty, so that the energy dissipation of pulse is on the direction of cutting.Therefore, when at the cut direction removing materials, be not that energy is focused on the roundlet luminous point, ellipse or rectangle luminous point with the energy dissipation of each pulse to lower energy density.For instance, can through construction, make rectangular long side direction on the direction of cutting by the rectangular beam of adjusting shape.

Although above-mentioned execution mode has been narrated about the unification semiconductor wafer, the technical staff will understand that other application, for instance, and internal memory reparation and laser electrical micro-machine.For instance, Fig. 9 is the electron micrograph of micromechanics pattern 900 in semi-conducting material that uses above-mentioned laser ablation methods.Example pattern 900 comprises about 51 microns wide ditches 902, and it is cut with an accurate pattern.Ditch 902 has the smooth in fact bottom sidewall good with definition.Moreover the distance 904 between ditch is approximately 25 microns so little.

The technical staff will be appreciated that from the announcement at this, also can realize other pattern or cutting more accurately.For instance, Figure 10 is the electron micrograph of micromechanics pattern 1000 in semi-conducting material that uses above-mentioned laser ablation methods.Example pattern 1000 comprises about 50 microns wide ditches 1002, and it isolates some positions 1004 by about 10 microns wide distances.

In Fig. 7,8 and 9, what can find is there is no in fact chip, crack or pollutant.In specific implementations, need some to clean to remove chip in a small amount.For instance, after traditional water under high pressure or solid carbon dioxide " sandblast " technology can be used in laser ablation, to remove particle or chip.Yet compared with conventional laser or mechanical saw cutting technique, assisted ablation step described herein is normally comparatively clean, and compared with traditional step, only needs less cleaning or do not need cleaning fully.Therefore, do not need for cut step be provided at element on wafer between additional lateral separate.Moreover, owing to using low energy densities together with the short wavelength, tail off in the problem aspect heat affected area, crack, bits skin and chip.Therefore, obtain higher breaking strength and global procedures output.

That significantly for the details of above-mentioned execution mode, many changes can be implemented, and do not deviate from basic principle of the present invention for the people who is good at this technology.Therefore, category of the present invention should only can be determined by claims.

Claims (21)

1. a cutting is formed on the method for several layers on substrate, and the every one deck in several layers has the Laser Ablation Threshold that changes with laser pulse width separately, and the method comprises:

Determine the minimum laser ablation threshold of the every one deck in several layers;

Select soprano in the minimum laser ablation threshold;

Produce one or more laser pulse beams, the scope of the energy density that the laser pulse beam has is between the selected Laser Ablation Threshold of selected Laser Ablation Threshold and 10 times, and,

Delineate otch between several integrated circuits in being formed at several layers, otch passes several layers until the upper surface of substrate,

Wherein the scope of the aggregate thickness that has of several layers is between 8 microns to 12 microns.

2. the method for claim 1, wherein the scope of the pulse duration that has of laser pulse is between 0.1 psec to 1000 psec.

3. the method for claim 1, wherein the scope of the pulse recurrence rate that has of beam is between 100 KHz to 100 MHz.

4. the method for claim 1, wherein the energy range of each pulse is between 1 little joule to 100 little joules.

5. the method for claim 1, wherein the average energy scope of beam is between 10 watts to 50 watts.

6. the method for claim 1, wherein with the speed of scope between 200 mm/second to 1000 mm/second, the otch of several layers is passed in delineation to beam through construction.

7. the method for claim 1, further comprise along the length direction of otch saw cutting substrate.

8. the method for claim 1, wherein otch forms the first delineation line and the second delineation line, and it separates the first active component zone from the second active component zone.

9. method as claimed in claim 8, further be included between the first delineation line and the second delineation line, cuts several layer and substrates with saw.

10. the method for claim 1, further comprise with the cutting of beam single track and pass several layer and substrates.

11. the method for claim 1 comprises that further controlling beam shape provides uniform radiation form.

12. the method for claim 1, wherein in several layers comprises low k dielectric material at least.

13. the method for claim 1, wherein the scope of the energy density that has of laser beam is between the selected Laser Ablation Threshold of selected Laser Ablation Threshold and five times.

14. the method for a wafer scribing, on this wafer or wherein form several integrated circuits, integrated circuit is separated by one or more roads, and the method comprises:

Produce one or more laser pulse beams, the selectable pulse duration of this laser pulse tool is in order to minimize the ablation threshold of target material; And,

With the target material of a beam ablation part, the range of pulse repetition frequency of its beam between 5.1 MHz to 100 MHz,

Wherein the scope of the thickness of target material is between 8 microns to 12 microns.

15. method as claimed in claim 14, wherein pulse width range is between 0.1 psec to 1000 psec.

16. method as claimed in claim 14, wherein the energy range of each pulse is between 1 little joule to 100 little joules.

17. method as claimed in claim 14, wherein with the speed of scope between 200 mm/second to 1000 mm/second, target material is passed in cutting to beam through construction.

18. the method for a wafer scribing, on this wafer or wherein form several integrated circuits, integrated circuit is separated by one or more roads, and the method comprises:

Produce one or more laser pulse beams, this laser pulse has the scope of pulse duration between 0.6 psec to 190 psec; And,

With the target material of a beam ablation part,

Wherein the scope of the thickness of target material is between 8 microns to 12 microns.

19. method as claimed in claim 18, wherein beam has the scope of pulse repetition frequency between 100 KHz to 100 MHz.

20. the method for a wafer scribing, on this wafer or wherein form several integrated circuits, integrated circuit is separated by one or more roads, and the method comprises:

Produce one or more laser pulse beams, this laser pulse has the scope of pulse duration between 210 psec to 1000 psecs; And,

With the target material of a beam ablation part,

Wherein the scope of the thickness of target material is between 8 microns to 12 microns.

21. method as claimed in claim 20, wherein beam has the scope of pulse repetition frequency between 100 KHz to 100 MHz.

Images